Saturated polyester useful as low shrink additive for molding compositions containing unsaturated polyesters

ABSTRACT

Disclosed are linear saturated polyesters that can be added to unsaturated polyester resins to prepare a molding composition that exhibits an unobviously low shrinkage upon curing. The linear saturated polyesters are prepared from terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, diethylene glycol and benzenetricarboxylic acid.

United States Patent [1 1 [111 3,929,868

Dombroski et al. Dec. 30, 1975 [5 SATURATED POLYESTER USEFUL AS LOW 3,390,132 6/1968 Walker 260/75 SHRINK ADDITIVE FOR MOLDING 3,391,056 7/1968 Robinson.. 161/232 3,489,707 1/1970 Fry 260/3l.6 COMPOSITIONS CONTAINING 3,553,284 1/1971 Riemhoferet a1... 260/850 UNSATURATED POLYESTERS 3,642,683 2 1972 Fry 260/31.6 [75] Inventors; John Dombmski; John 3,736,278 5 1973 Wada 260/22 CB Caldwell, both of Kingsport, Tenn.

[73} Assignee: Eastman Kodak Company, Primary Examiner Dona1d CZaJ-a Rochester Assistant Examiner-Earl A. Nielsen [22] Filed: Iuly 11, 1974 [21] Appl. No.: 487,691

Related U.S. Application Data ABSTRACT [63] Continuation-impart of Set. N6. 388,705, Aug. 15,

1973, abandoned. Disclosed are linear saturated polyesters that can be added to unsaturated polyester resins to prepare a [52] US. Cl 260/475 P; 260/75 R molding composition that exhibits an unobviously low [51] Int. Cl. C08G 63/20 shrinkage upon curing. The linear saturated polyesters [58] Field of Search 260/75 R, 475 P are prepared from terephthalic acid, isophthalic acid, l,4-cyclohxanedicarboxylic acid, diethylene glycol [56] References Cited and benzenetricarboxylic acid.

UNITED STATES PATENTS 2,856,378 10/1958 Lundberg 260/3l.6 2 Claims, l Drawing Figure LINEAR SHRINKAGE MILS/ IN.

MOLECULAR WEIGHT of LINEAR SATURATED POLYESTER U.S. Patent Dec. 30, 1975 MOLECULAR WEIGHT of LINEAR SATURATED POLYESTER SATURATED POLYESTER USEFUL AS LOW SHRINK ADDITIVE FOR MOLDING COMPOSITIONS CONTAINING UNSATURATE POLYESTERS Other prior art that applicants are aware of is US. Pat. Nos. 2,642,403, 3,489,707, 3,549,586, 3,642,683, 3,668,178, 3,701,748, 2,856,378, 3,642,672, 3,736,278, 3,607,530, Belgium 741,777 and Belgium This application is a continuation-in-part O Our U.S. Pat. No. 2,856,378 is distinguishable from this pending apphcatlon Serfi g invention because this reference does not disclose the 1973, now abandoned. alicyclic dicarboxylic acid used in the saturated linear This invention relates to specific linear saturated ol ter, polyesters that can be added to unsaturated polyester 1 U,S P t, N 3,736,278 i di ti gui h d f om thi resins Prepare F g cofnpositiPns that exhibit invention because this reference discloses only polyesunobvlously W hri ag dllflng Cllflflgters of neopentyl glycol and propylene glycol.

Unsaturated Polyester molding compositions are US. Pat. Nos. 3,549,586 and 3,668,178 are distinwidely used today. T ese mpo iti n when Cured guishable from this invention because these references under heat and pressure,produce rigid thermoset proddi lo only polyesters of hydroxyacids, such as aucts which have found broad application in the manuh d caproio id facture of automotive parts, bo s, ppl P We have now invented specific linear saturated polyfllmlture, Although Q glasstemforced esters that can be added to glass filled unsaturated saturated polyester mo ding COmP produce polyester resins to prepare molding compositions that molded articles that have an acceptable surface finish, hibi b i l l h i k upon i g nd the use of fiber glass reinforced unsaturated polyester n quently exhibit exceptionally high surface molding compositions in applications requiring excelooth lent finished appearance has been restricted because of The linear saturated polyesters of this invention can the inherently poor surface quality of molded parts. be described as polyesters consisting essentially of the The unacceptable surface characteristics of fiber glass 5 following structure herein reinforced moldings often necessitate costly prepamt w operations, such as sanding and abrading, in order to bafsed 2 33 2 c ig 33 a obtain acceptably smooth painted products. 9; 2 3 ls mm 0 mo es an The unacceptable surface character is thought to th fd d I result from shrinkage which occurs in the unsaturated or e S or an 6 sum 0 an f1s0or1,g1s00rlandthesumoffandgl, polyester-monomer crosslmklng reaction. According e orf are at least 1, the molecular weight of the polyto one theory, the areas between the glass fibers at the ester is 4000 to 6000, and surface take the form of depressions because of the the acid number of the polyester IS 10 to 30. contraction of the resin during curing. As is well known The low shrink molding composition obtained by in the art, a typical unsaturated polyester resin Shl'lIlkS bout 8 107 b vol e I din tic! S adding the linear saturated polyesters to an unsaturated a 0 y ume as l n mo at e polyester resin can be described as a curable composiof typical sizes, this can result in an overall llnear part tron comprised of an admixture of shrinkage of from l-4 mils/1n.

T h f d th h k f t A. an unsaturated polyester,

ratei'l p i y e st er :2sirf u ssh uri g aie re gcfrtzd i2 8 S a monomer having at least one olefinic group h t t t d l t Pat. Nos. 3,642,672, 3,549,586 and Netherlands zgg he e yes er 67/10031. These techniques mvolve adding to Itlhehun- C from 8 to 16 weight percent, based on the weight saturated polyester resin a high molecular welg t t erof the composition, of the linear Saturated polyes moplastic polymer, such as homopolymers of various ten acrylates, methacrylates, styrene and vinyl acetate, copolymers of styrene, copolymers of vinyl chloride and vinyl acetate, cellulose acetate butyrate, cellulose acetate propionate and others.

As can be readily understood from examining the above structure, the linear saturated polyesters are prepared from terephthalic acid, isophthalic acid, 1,4-

cyclohexanedicarboxylic acid, diethylene glycol and benzenetricarboxylic acid or the corresponding acid anhydrides. The benzenetricarboxylic acid can be either the 1,2,4-isomer, sometimes called trimellitic acid or the 1,3,5-isomer, sometimes called trimesic acid or the anhydrides of these acids.

The linear saturated polyester can be prepared by a process comprised of two steps.

The first step in the process for preparing the linear saturated polyesters is preparation of a hydroxy terminated polyester from terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxy1ic acid and diethylene glycol. These hydroxy terminated polyesters can readily be prepared by those skilled in the art by determining the amount of the various materials needed to achieve the above-described quantity of moles in the structure and then forming the hydroxy terminated polyester according to techniques well known in the art, such as ester interchange, direct esterification as acidolysis. The molecular weight must be controlled so as to achieve a molecular weight of 4000 to 6000 in the final linear saturated polyester.

The second step in the process for preparing the linear saturated polyester is to carboxylate the ends of the hydroxy terminated polyester with sufficient benzenetricarboxylic acid to achieve an acid number of to 30. Thus, only a portion of the hydroxy ends will be reacted with the benzene tricarboxylic acid.

In this invention, the molecular weight of the linear saturated polyesters are critical. In general, if the molecular weight is either too high or too low the molding composition containing the linear saturated polyesters will not exhibit unobviously low shrinkage upon curing. The attached FIGURE provides a quantitative expression of this phenomenon. It is to be observed in the FIGURE that the range of molecular weight of the linear saturated polyester is indeed critical. Specifically, it is to be observed that within the range of 4000 to 6000 the linear shrinkage is not greater than about 20 mils/inch and within the range of 4600 to 5800 the linear shrinkage is not greater than 16 mils/inch. Further, within the range of 4800 to 5500 the linear shrinkage is not greater than about 12 mils/inch and at about 5250 molecular weight the linear shrinkage is reduced to a minimum value in the order of 10 mils/inch. In contrast, beyond the range of 4000 to 6000 the linear shrinkage generally varies between values in the order of about 20 to 24.

In this invention the acid number of the linear saturated polyester is from 10 to 30. If the acid number is below about 10 or above about 30 the surface of articles molded from the unsaturated polyester exhibit a poor surface finish.

The unsaturated polyesters useful in this invention are well known in the art and can be prepared from dicarboxylic acid components and diol components such as described in US. Pat. Nos. 3,642,672 and 3,549,586, herein incorporated by reference. Typically, the unsaturated polyester is prepared from a dicarboxylic acid component comprised of an ethylenically unsaturated anhydride containing 2 to 10 carbon atoms, and a diol containing 2 to 10 carbon atoms. In a particularly preferred embodiment of this invention, the dicarboxylic acid component is maleic anhydride and the diol is propylene glycol.

The monomer having at least one olefinic group copolymerizable with the unsaturated polyester is well known in the art and is described in US. Pat. Nos.

3,642,672 and 3,549,586, herein incorporated by reference. Styrene is a particularly preferred monomer.

The linear saturated polyester can be in the range of from 8 to 16 weight percent, based on the weight of the composition and preferably is in the range of from 9 to 12 weight percent, based on the weight of the composition.

The unsaturated linear polyester can be admixed with the other materials to form the molding composition by conventional means.

The following examples are presented to illustrate but not limit the invention.

EXAMPLE 1 This example illustrates preparation of the linear saturated polyester of this invention.

Forty three and seven tenths grams of dimethylterephthalate (0.255 mole), 43.7 g. of dimethylisophthalate (0.255 mole), 10.0 g. of 1,4-dimethylcyclohexane dicarboxylate (0.05 mole), 79.6 g. of diethylene glycol (0.75 mole) and ppm. Ti as titanium tetraisopropoxide in butanol were placed in a flask and heated with stirring to 200C. The ester interchange reaction was rapid and after 2 hr. the temperature was increased to 250C. The reaction was further heated at this temperature for 2 hours under a stream of nitrogen. A vacuum was then applied to remove excess glycol over a period of /2 hr. and the pressure was further reduced to 0.20 mm. while the reaction was stirred and heated at 250C. for 2 hours. The viscous polymer was removed from the flask at atmospheric pressure under a stream of nitrogen. One hundred fifty grams of the polyester, having a number average molecular weight of 5,864 was carboxylated with 1.71 grams of trimellitic anhydride by heating the polymer, 1 hr. at 250C. under a stream of nitrogen to form the linear saturated polyester of the invention having a molecular weight of 5,256 and acid number of 1 1.2.

EXAMPLE 2 This example illustrates the ability of the linear saturated polyester prepared in Example 1 to reduce the shrinkage and modify the surface appearance of a cured unsaturated polyester.

A first sample illustrating the molding composition of the invention was prepared with the following composition:

44.5% poly(propylene glycol maleate) unsaturated polyester 44.5% styrene 10.0% saturated linear polyester (from Example 1) 1.0% benzoyl peroxide A second sample was prepared with the same ratio of unsaturated polyester and styrene, but without the saturated linear polyester.

Both the first and second samples were degassed and decanted into the cavity of a precision machined stainless steel mold. Cure was effected by heating the mold in a water bath at 100C. for 15 min. After cooling to room temperature, the diameter of the thermoset samples were measured with a micrometer and shrinkage was calculated relative to the inside diameter of the mold. The thermoset sample molded from sample one illustrating the molding composition of the invention had low shrinkage and a smooth, glossy surface, while the thermoset sample molded from sample two had high shrinkage and a cracked, rough finish. Table 1 below summarizes the shrinkage and surface characteristics of the thermoset samples molded from samples 1 containing 70% styrene one and two. 7 5 CaCQ3 TABLE 1 0.18 lb. zinc stearate Linear Shrinkage 5 0.05 lb. t-butyl perbenzoate s 1 N PP i Th S l 0.24 lb. Modifier-M, a thickening agent commeramp 8 ermose amp e ermose ampe cially available from Marco Resins Div., W. R.

l Opaques, Wkhite, l0 mils/in. Grace C l gfi fig lb. glass fibers (l in. length) 2 Transparent, 44 10 The fiber reinforced molded parts exhibit very little rac Rough surface shrinkage and exhibited a smooth, uniform surface.

We claim: EXAMPLE 3 1. A polyester consisting essentially of the following This example illustrates the low shrink and desirable structure H V I .1 o

HO-CHzCl-IzOCHzCHz of E -fi-O-CHzCHzOCHzCHz o 3 fi-O-CHzCHzOCHzCHa o o d to H e l i1, Q O-O O? -T n-EOCH2CH2OCH2CH2 O- -0 'EO-CH2CH2OCH2CH2 O- OH O O b o o O surface characteristic of fiberglass reinforced articles wherein molded from the molding composition composed of the based on the sum of a, b and c being 100 moles, a is linear saturated polyester and an unsaturated polyester from 44 to 47 moles, b is from 44 to 47 moles and resin. c is from 6 to 12 moles,

Sheet molding compositions are prepared with the d is 0 or 1, e is 0 or 1 and the sum of d and e 1, following materials: fis 0 or 1, g is 0 or I and the sum off and g I,

3 lb. KopLac 3701-25, a poly(propylene glycol malee orfare at least 1, the molecular weight of the polyate) unsaturated polyester resin containing 70% ester is 4000 to 6000, and styrene, and commercially available from Koppens the acid number of the polyester is 10 to 30. Chemical, Inc. 2. The polyester of claim 1 wherein the molecular 2 lb. linear saturated polyester prepared in Example weight of the polyester is 4800 to 5500. 

1. A POLYESTER CONSISTING ESSENTIALLY OF THE FOLLOWING STRUCTURE WHEREIN BASED ON THE SUM OF A, B AND C BEING 100 MOLES, A IS FROM 44 TO 47 MOLES, B IS FROM 44 TO 47 MOLES AND C IS FROM 6 TO 12 MOLES, D IS 0 OR 1, E IS 0 OR 1 AND THE SUM OF D AND E=1, F IS 0 OR 1, G IS 0 OR 1 AND THE SUM OF F AND G=1, E OR F ARE AT LEAST 1, THE MOLECULAR WEIGHT OF THE POLYESTER IS 4000 TO 6000, AND THE ACID NUMBER OF THE POLYESTER IS 10 TO
 30. 2. The polyester of claim 1 wherein the molecular weight of the polyester is 4800 to
 5500. 